A map released by Maurice Blackburn shows the projected extent of flooding if Wivenhoe Dam had been differently managed. Bright green spots indicate areas the modelling says would have been spared flooding, and yellow spots are areas that would have flooded had Seqwater operated the dam "properly".
Supplied: Maurice Blackburn

Thousands of people have signed on to a possible class action against the Queensland Government for damages incurred in the 2011 floods.

Damian Scattini from Maurice Blackburn says a report by US hydrologists claims the operators of Wivenhoe Dam were negligent and caused unnecessary damage.

"They held too much water in the reservoir for too long, and then when they realised what they'd done, they panicked and released too much at once," he said.

Maurice Blackburn and IMF Australia have received interest from about 4,000 flood victims, mainly in Brisbane and Ipswich.

John Walker from IMF Australia says the case could be one of the biggest of its kind in Australia.

"We don't know to a large extent what losses each of those people have had. We've worked it out in a broad sense," he said.

"In the next two to three months we'll be seeking to get a clear understanding of the losses associated with this flood that didn't need to occur."

The lawsuit has a budget of $10 million and if successful, the compensation could run into the billions of dollars.

Seqwater says it is confident the dam was properly managed during the flood crisis.

The company says its view has been supported by a range of independent and leading dam experts.

Lawyers say they will know within a couple of months whether they have enough support to continue with the action which could take up to four years.